The present invention concerns an apparatus for the propagation of the rotary twisting of a yarn in a thread guide to the entwinement point in a open-end spinning machine having an open-end spinning element and concerns also a process which can be carried out with the aid of an apparatus of this type.
It is a matter of great importance in an open-end spinning machine, that at the point of yarn entwinement in which, during the yarn formation process, running fibers are forming into an open yarn-end, that sufficient rotation is provided to avoid a break in the newly incorporated yarn. To accomplish this, it is a conventional practice to interpose a device into an open-end spinning element in which the yarn is being made. This device, because of its structure and profiling, causes a periodic lifting of a yarn as it is being led through a thread guide at a change-of-direction surface of a thread intake element called a thread withdrawal nozzle. This lifting is done to enable the rotational twisting to propagate itself back to the entwinement point. Due to this profiling, however, the uniform twisting of the yarn seized in the withdrawal nozzle at the entrance to the thread guide, or within the thread guide, is detrimentally affected by temporary restraint and subsequent release of the yarn with the result that the surface of the produced yarn is roughened. In order to hold this undesirable side effect to a minimum an additional dummy rotator is provided in the thread guide, in order to increase the twist, so that, upon the true twist, a false twist is superimposed. On the grounds of the increased twist within the thread guide, the change-of-direction surface is to be more easily overcome. Further, the twist which builds itself up from the true twist and the false twist can propagate itself better back to the fiber entwinement point.
The principal object of the present invention is first, to create a possibility of achieving a good rotational propagation within the open-end spinning element, and second, to provide protective treatment of the yarn. Additional objects and advantages of the invention will be set forth in part in the following description or may be obvious from the description, or may be learned through practice of the invention.
This object is achieved by providing, in the longitudinal extent of the thread guide, a thread contact surface, in which a vibration element is installed. Since the yarn, upon its withdrawal in the course of its rotation in the thread guide, is not held back by a mechanical restraining element, the yarn is subjected to no high mechanical stress and its surface is not damaged. Further, because of the oscillation imparted to the yarn from the vibration element, the yarn is periodically lifted from the thread contact surface, so that the rotation during this phase can propagate effectively without hindrance in the direction toward the fiber entwinement point.
The thread contact surface can be an element independent of the thread guide, however, it may be advantageous, if this thread contact surface is part of the thread guide and the surface is an integral part of the thread guidance system.
Since it is particularly important that the twisting, which forms in the thread guide, propagates to the fiber entwinement point in order to encourage the fiber incorporation into the yarn end, provisions in an advantageous embodiment have been made so that the thread contact surface, which has been set into vibration, is positioned in the nearest possible location to the spinning element. To properly position the thread contact surface in such a manner, the thread contact surface may be a part of an inlet element on the thread inlet end of the thread guide.
An optimal release of the yarn can be achieved by having the inlet element stimulated by the vibration element in an axial direction.
It is true, that for the acquiring of special surface characteristics in the formed yarn, now as before, it is possible to install a thread contact surface with a profiled face. Yet, for the object of the invention, which is the propagation of the rotational twisting, such a designed surface is not required and as a rule, a smooth outer surface design which possesses a polished surface is preferred.
Principally, any optional vibration drive for producing the oscillations can be applied, but an electromagnetic drive has shown itself to be particularly advantageous.
For the achievement of an optimal result, in regard to the character of the yarn as it is made, an advantageous improvement of the invented apparatus allows various degrees of oscillations to be selected by connecting a control system to the vibration element for the control of frequency and/or amplitude. In connection with the control system, it is favorable for the simplification of the apparatus, if the control system is furnished with a multiplicity of vibration elements.
With the aid of the apparatus in accord with the invention, it becomes possible, not only to impart vibration to the yarn, and thereby to improve the propagation of twisting, but moreover, this control system can be made to coincide with the current operational phase. Thus, it is not a requirement during the start-up of spinning and during normal production to have always the same vibration brought to bear. During the start-up phase, a defined vibration, perhaps with a lower frequency and a reinforced amplitude, can be brought into action on the yarn. In this way, the twisting engendered in the thread guide can be transmitted in good order to the entwinement point. Subsequently, during the normal, undisturbed production, another vibration characteristic is applied, since the vibration in regard to frequency and amplitude is made to suit the altered spinning conditions, for example by increasing the frequency and amplitude. In a similar way, the oscillation characteristic of the speed of rotation of the spinning element, i.e., of the rotating force therein, can be matched and/or made to suit the fiber material to be spun.
In the concept of the present invention, the idea of xe2x80x9cRate of rotation of the spinning elementxe2x80x9d does not encompass only the RPM of a mechanical spinning element, but should, in many cases, also include the rotation speed of a pneumatic or electromagnetic vortex, which actually depends upon the individual design of the open-end spinning apparatus.
With the invention""s aid, the twisting propagation to the entwinement point is improved, without a situation wherein the surface of the produced yarn must suffer, since the yarn, during its withdrawal in the longitudinal zone of the thread guide, generally passes therethrough over a predominately smooth surface. A false rotational element, on this account, can be dispensed with, insofar as the twist propagation to the entwinement point is concerned. Except in a protective treatment of the yarn captured in the withdrawal, the special advantage of the invented process and the invented apparatus, above all, can be seen in that the twist propagation to the entwinement point is carried out independently of the rotational speed of the open-end spinning element. Further, the characteristics of the vibration, regarding frequency and amplitude can be chosen freely in accord with the desired spinning conditions. As stated above, the choice is independent of the rotational speed of the spinning element, and is independent of the medium or magnetic forcefield which rotates therein. In this way, the process and the apparatus of the present invention make possible the matching of the twisting propagation to the current operation phase, to the spinning fiber material and the ongoing operational speed. Thus, during the entire spinning procedure, in spite of different spinning conditions, optimal relationships are always available for the propagation of the rotational twist.
Embodiment examples of the invention are explained below with the aid of the drawings.